No longer needed by group - a stand-in (4)
I believe the answer is:
past
'no longer' is the definition.
'by group a stand-in' is the wordplay.
'in' says the answer is hidden in the clue.
'PAST' is hidden within 'by group a stand'.
'needed' is the link.
(Other definitions for past that I've seen before include "Gone by in time" , "A person's earlier life history" , "Finished, gone" , "historical times" , "Bygone" .)